Hydrogen Oxygen Catalytic Combustor for Fuel Cell Water Management
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Solution Overview
Problem
Fuel cell power plants face challenges in maintaining water above freezing temperatures without electricity, especially in subfreezing environments, and existing catalytic combustors operate inefficiently due to reliance on electrical controls and high temperatures.
Innovation Solution
A hydrogen/oxygen catalytic combustor using a porous metal substrate with a temperature-responsive mechanical valve and oxygen diffusion control device, which operates without external power, maintaining water above freezing by combusting hydrogen and oxygen while preventing water entrainment and ice formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a catalytic combustor operates at high temperatures (93-370°C) to maintain water above freezing, then the water management function is achieved, but the combustor operates inefficiently and consumes excessive energy
Solution Approach 1:
The patent changes the operating temperature parameter of the catalytic combustor from the conventional high range (93-370°C) to a lower range (above ambient but below freezing point of water in accumulator). This parameter change allows the combustor to operate more efficiently while still achieving the desired heating effect through the thermal mass of the water in the accumulator, thereby reducing energy consumption.
2Measurement precision
If electrical controls are used to manage the combustor and temperature sensors, then precise temperature control is achieved, but the system becomes complex and requires external power which may not be available during shutdown
Solution Approach 1:
The patent employs a self-service mechanism where the water in the accumulator serves as both the medium to be heated and the temperature sensing element. When the water temperature drops to the freezing point, the water itself indicates this through phase change or temperature-dependent properties, eliminating the need for external electrical temperature sensors and control systems. This simplifies the device while maintaining effective temperature management.
Solution Approach 2:
The patent uses an intermediary substance (such as a salt solution or antifreeze agent) in the accumulator that has a known freezing point. This intermediary acts as a passive temperature indicator - when the temperature reaches the freezing point of the intermediary, it provides a measurable signal (phase change, conductivity change) that triggers the combustor operation without requiring complex electrical sensing systems.
3Reliability
If water is drained from the system during shutdown to prevent freezing damage, then mechanical damage from ice formation is avoided, but the system cannot quickly restart because ice must be melted in the accumulator and associated components
Solution Approach 1:
The patent applies preliminary action by maintaining a small amount of water in the accumulator and associated components during shutdown instead of complete drainage. The catalytic combustor operates periodically during shutdown to keep this water above freezing temperature, preventing ice formation in the first place. This preliminary heating action eliminates the need for time-consuming ice melting during startup while still protecting against freezing damage.
4Loss of energy
If the combustor is disposed within the insulated enclosure, then heat transfer to the accumulator is improved, but the temperature sensors and controller require electrical power which is not available during shutdown
Solution Approach 1:
The patent replaces the electrical control system with a mechanical or passive thermal system. The combustor is positioned within the insulated enclosure for efficient heat transfer, but its operation is controlled by passive thermal mechanisms such as thermal expansion of a bimetallic strip, thermal convection currents, or phase change of an intermediary substance, rather than electrical sensors and controllers. This substitution maintains effective heat transfer while eliminating electrical power requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables efficient catalytic combustion at lower temperatures, extending the life of the combustor and allowing fuel cell power plants to start quickly, even in freezing conditions, without electrical controls, ensuring efficient heat transfer and preventing ice buildup.
Implementation Method 1
a catalytic combustor which combusts hydrogen and oxygen to heat water in the accumulator
Implementation Method 2
one or more temperature sensors are disposed at various critical points within the enclosure, the temperature indicating signal(s) of which are provided to a controller which in turn controls either static or intermittent flow of hydrogen through a valve
Implementation Method 3
the heat being communicated via a small inlet duct or hood in the lower portion of the enclosure
Data Source
AI summary
Water in a fuel cell accumulator is kept above freezing by a hydrogen/oxygen catalytic combustor fed hydrogen through a mechanical thermostatic valve in thermal communication with the container and connected to a hydrogen supply. The system includes an ejector hydrogen/oxygen combustor and a diffusion hydrogen/oxygen combustor for warming a medium within a container such as water in the accumulator of a fuel cell in response to a mechanic hydrostatic valve which conducts hydrogen to a combustor responsive to the temperature of the container.